INTRODUCTION:

One year, 900 locations, thousands of coral reefs. That's the tally of NASA's Landsat 7 satellite as it continues to deliver cutting edge images and information about the Earth. Data being presented this week at an international conference in Indonesia is the first assessment of the physical condition of major reefs from the the new Landsat 7 collection of images. More than 5000 coral reef scenes have been amassed in the first year of Landsat 7's operation. In that collection, many reefs have been seen more than once, offering scientists an opportunity to study seasonal variations as well as other changes in the reefs caused by hurricanes and climate change.

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TELLING THE TALE OF AN ATOLL

These elegant whorls of color are atolls, enclosed coral reefs almost always surrounding a lagoon. Generally speaking, atolls are the products of volcanic islands that have eroded away.

In general the process is believed to work like this. Coral forms off shore from volcanic islands in tropical latitudes, developing a barrier reef that's separated by a growing lagoon. But over time, while the surrounding ocean wears away the main body of the island, the coral ring remains. When the island ultimately disappears from view, the remaining lagoon is left with a protective atoll.

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SPIRES OF LIFE

These images from the Landsat 7 satellite depict a number of coral reefs like delicate brush strokes of color against an indigo canvas. Landsat 7 "sees" the Earth differently than a camera. By detecting light in discretely separate ranges of color or more accurately, electromagnetic bands the instrument can tailor images to highlight particular features being studied by experts. The different shades in these images highlight various features specific to each coral colony. Patches of bright red show places where coral reefs are actively populated with living organisms.

The bands of color in the first image show "natural color", essentially the colors we would see if we could look down from Landsat 7 ourselves. But in the second image, an exchange of the visible light red band for one that sees near infrared data instead makes some areas on the reef jump out in bright red relief. The near infrared band best gathers the electromagnetic signature of a thriving ecosystem. In these images where there is not a red signal, the coral is not actively growing.

It's important to remember that much like the bark of a tree is primarily the only actively growing part of the organism, not all of the area of a coral reef needs to be growing to indicate health. Living coral makes its home on the ancient beds of ancestors, which essentially provide a foundation for newer generations to anchor themselves.

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CALCIUM COMMUNITIES

Coral is the ocean's architectural memorial to the lives of deceased coelenterates. The word "coelenterate" refers to the central body cavity found in the creatures. Located in tropical latitudes, the hard structures we know as coral are really the incremental build-ups of calcium carbonate deposited from the skeletal remains of these tiny colonial animals.

In many parts of the world coral is threatened from a variety of causes, some natural, some caused by people. By developing a global, searchable database of coral reefs based on state-of-the-art satellite data, researchers could have a powerful new tool for studying this vital and elegant part of the Earth's biosphere. This will help them not only develop better strategies for conservation, but help them refine methods for understanding what processes drive change in the world's oceans.

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DIVING FOR CORAL WITH A PLUNGE FROM SPACE

As scientists begin to map the world's coral, they're developing tools that can combine the findings of many different instruments into a comprehensive database. This visualization shows how that kind of synthesis might fit together.

More specifically, the purpose of this sequence is to demonstrate how different levels of resolution can contribute to a more refined total picture of what actually lives beneath the surface of the world's coastal oceans. The data sets are collected from the following sources, and listed with their corresponding levels of resolution:

SeaWiFS (NASA Instrument/U.S. Satellite): 1000 meters
MOS (German Instrument/Indian Satellite): 500 meters
Space Shuttle photograph: 30-50 meters Landsat 5 (NASA Instrument/US Satellite): 30 meters
AISA aircraft instrument: 5 meters
Benthic Habitats Map: 2-3 meters

The long, thin rectangle of data shown close to the ocean's surface is information collected from the aircraft. The motley pattern appearing underneath that stripe is a synthetic, analytic image created with software called Benthic Habitats. The software defines ocean environment characteristics down to the 2-3 meter range by combining information from various sources. Where the prior five levels of data are observational, captured by instruments flying above the research zone, the synthetic Benthic Habitats image comes analytic data, tailored in this case to the task of coral identification and research.

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SEAWiFS: INSTRUMENT AND LAUNCH

SeaWiFS is the scientific portion of the OrbView-2 satellite, orbiting The Earth at an altitude of 423 miles (705 kilometers). By providing a regular picture of the planet's color, SeaWiFS helps researchers learn about the state of the world's interconnected ecosystems. SeaStar blasted into space on August 1, 1997 lifted by an extended Pegasus rocket. SeaWiFS is considered a low cost mission, many orders of magnitude less expensive than earlier Earth observing instruments. One of its great assets is its full time dedication to a singular aspect of study, specifically ocean color. By exclusively focusing on color, the SeaWiFS project team has been able to concentrate their research into discrete, highly defined subjects.

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LANDSAT: INSTRUMENT AND LAUNCH

From an altitude of 438 miles (730 kilometers), Landsat 7 can see surface features as small as 15 meters, providing world-wide land resource information for a diverse range of uses. The satellite is part of a global research effort that NASA calls the Earth Science Enterprise, which seeks to acquire a long term understanding of the changes to our planet.

Landsat 7 is the latest in a series of satellites. It roared into orbit aboard a Boeing Delta II rocket on April 15, 1999 from Vandenberg Air Force Base in California. Managed and developed by NASAÕs Goddard Space Flight Center, Lockheed Martin constructed Landsat 7 at their facility in Valley Forge, Pennsylvania. Data is available to researchers through a browseable internet interface, and can be delivered at a relatively low cost to users.

NASA launched the first Landsat spacecraft on July 23, 1972.

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RESEARCHING CORAL REEFS FROM SPACE

Part of the problem in studying the health of the world's coral is the lack of a comprehensive database. Many experts consider the current standard to be imprecise, incomplete, and unreliable for the kind of detailed, modern analysis that's required for monitoring coral health around the world. But using a new program written in the computer language Perl for the World Wide Web, developers at the Goddard Space Flight Center have designed a browsable system that can access a wide range of data. The program is dynamic in the sense that as researchers collect varying resolutions and types of data from different parts of the world, the database can store and cross-reference all the available information. Heavily studied regions will have detailed and complex layers of data available, while less well observed areas will simply be catalogued with as much information as is available. As the system evolves, itÕs expected to develop into a huge data repository regarding coral around the planet. As a natural by-product it will also collect other vital oceanographic information gathered at varying levels of spatial resolution.

The searchable coral database is still a work in progress, but it's available for consideration at http://seawifs.gsfc.nasa.gov/reefs The following poster shows how several instruments with different spatial resolutions can be used for studying coral reefs. Goddard's scientific and Visualization Studio developed the poster in collaboration with members of the SeaWIFS Science Team.